Both the rear dropouts are replaceable on the Edit, Filter and Bitmap. It's one of those little extra touches that we think are important. It's particularly important to have a replaceable mech hanger because your fancy new clutch mech hangs off the side of the bike where it's vulnerable to rock-strike. If that happens, you don't want your mech to snap or your frame to be damaged. Much better to replace the dropout, which is designed specifically for that purpose.
